question

My reasoning is my generator, current split phase shore power and solar controllers would be feed into the autotransformer and the output would be a stable and balanced split phase 120V

1) Solar controllers are best fed direct to the battery as dc.

2) Whilst an auto transformer will try to balance leg currents, it won't stabilise the voltage.

3) For Shore power safety, and to meet ridiculously low RCCB currents (4mA) in some shore installations, you will need an ISOLATING transformer - not an auto transformer. The isolating transformer can be would to give the same balancing function as an autotransformer, but will have 2 sets of windings.

4) If the generator has a centre tap, then there is no need to run this through a transformer too.

I’m not sure about any of the “split phase” description but as previously mentioned, if a transformer was fitted it should be an isolation transformer. The reasons for this can get a little complex so if you are considering a rebuild I suggest getting some advice from a respected marine electrician. You have not mentioned if the yacht is fibreglass, timber, steel or aluminium but these are important considerations when designing your electrical fit-out.

One thing you may consider however, is if you really need to plug into shore power at all. You didn’t mention the size or style of the boat which may have a bearing on my next comment. We have lived on our boat for extended periods and we have enough solar to not require plugging in to shore power. This can change your design if you do not really need to plug into a marina. If you are circumnavigating you will spend a lot of time away from a marina so maybe you can commit to simply being self sufficient. If that is the case the need for the isolation transformer goes away.

Do you have any 240 volt loads ?

Thanks everyone, I see my confusion, and apologies for not providing a clear question to the forum. I have come to the conclusion that I do not need a Autotransformer because both my Shore Power Pedestal and Generator are 50 Amps which provide a Line1 @ 120v and L2 @ 120v. I do not have any 240v Loads but need the Line1 to power my Multiplus II Charger / Inverter and Line2 to power my second Multiplus II Charger / Inverter. The Neutral is shared.

Thanks again and apologies for the confusion.

Cheers.